Joe Schmidt has defended pairing inexperienced centres Robbie Henshaw and Jared Payne against South Africa rather than pressing Gordon D'Arcy into action.

Ireland boss Schmidt has long since identified Connacht's Henshaw and Ulster's Payne as the two men to fight it out to replace now-retired talisman Brian O'Driscoll.

Schmidt admitted the decision to pair the two men in a new-look midfield proved a surprise even to himself, given he had expected D'Arcy to be ready to start the autumn Test series.

The Kiwi head coach revealed Leinster stalwart D'Arcy has actually shaken off a calf problem - just not in time to be reasonably considered to face the Springboks in Dublin on Saturday.

Ireland must wait a little longer to discover the great successor to O'Driscoll, then, but Schmidt backed debutant Payne and 21-year-old Henshaw to forge a threatening partnership.

"It was what was available to us at the start of the week," Schmidt said of the Henshaw-Payne pairing.

"Robbie Henshaw's flexibility to play 12 or 13 is similar to Jared Payne, but that's the way they trained last week, so we've decided to go with that.

"Gordon was injured last week. He's probably back to full fitness now but we weren't absolutely sure of that at the beginning of the week.

"We have very small windows of preparation so we just felt we were partway along a pathway that was looking reasonably positive.

"We thought Gordon would be fit. He probably has made it, to be fair to him, but we hadn't had any time with the combinations.

"It was going to be a new pairing no matter what, so we just decided to go with what had been working together."

Athlone-born Henshaw will start at inside centre with 79-cap D'Arcy not included in the match squad at all.

Ireland swept to last term's RBS 6 Nations with a centre pairing boasting a closing tally of 212 caps - against the Springboks Schmidt's midfield will start the day with a combined Test total of just three appearances.

Henshaw will line up against South Africa captain and 102-cap veteran Jean de Villiers, underlining the size of the task facing Ireland's new centre partnership.

Former New Zealand Under-21 cap Payne will make his Ireland debut after qualifying through residency, the 29-year-old having signed for Ulster in 2011.

Schmidt expects D'Arcy to feature across the later autumn clashes against Georgia and Australia.

The ex-Clermont and Leinster coach admitted to being excited to see Ireland's bulked-up midfield in action against the gritty Springboks, but warned aggression requires as much mental fuel as physical.

"Ireland have been blessed with a centre pairing for a huge length of time that has not necessarily been the biggest but has been as physical as the best," said Schmidt, praising D'Arcy for mentoring the new midfield duo.

"Physicality is sometimes determined by the will rather than the size.

"Hopefully on Saturday we'll get a bit of both from our centre pairing.

"To be fair to Gordon D'Arcy, he has helped immeasurably. He's been a really good mentor for Robbie and Jared this week.

"To be honest, I didn't tell the centres in advance - I just named the team.

"It wasn't too much of a surprise to them because they'd been running in there together.

"I did speak to Gordon beforehand, and he's very much team-orientated as always.